body {
    width: 100%;
}
.image {
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
}
.container {
    position: absolute;
    width: 100%;
    height: 100%;
    text-align: center;
}
h1 {
    font-style: italic; 
    font-size: 80px;
    color: #ADD8E6;        /*light blue*/
    text-align: center;    /*此定义为水平方向*/
}
.input {
    width: 300px;
    height: 300px;
    font-size: 30px;
    position: center;  /*此center定义为垂直方向*/
    margin: 0 auto;  
}
.input_text {
    padding: 9px;      /*两方格之间的垂直距离*/
}
.btn {
    text-decoration: none;
}
.login_btn {
    font: 16px/20px Arial;
    border: 1px solid #DDD;
    padding: 5px 12px;
    margin-top: 20px;      /*登录按键与上面的间距*/
    background: #FFF;
    color: black;
}